1. Field of the Invention
The present invention is directed to a microscope illumination device for transmission viewing of an object to be examined, with a light source for producing a light beam, an optical arrangement for focusing the light from the light source via an objective lens on an object to be examined, and a reflector mechanism, which is located on an opposite surface of the object and for reflecting the illuminated light transmitted by the object back onto the specimen.
2. Description of the Prior Art
“Trans-illumination” of specimen in a microscope is usually accomplished through a condenser, which directs the light from a light-source through the specimen onto the objective lens, the latter being positioned on the opposite side of the condenser. In “epi-illumination”, on the other hand, which is needed for fluorescence or reflection microscopy, illumination occurs through the objective lens, i.e., is accomplished by the same optics by which the preparation is viewed. Preferably, xenon and mercury short arc lamps are used as the light sources. If the intention is to switch back and forth quickly between incident epi- and trans-illumination, it becomes noticeable that the indicated light sources cannot be turned on and off quickly or their intensity cannot be controlled. For a microscope with automatic control of all functions, for example, by a computer, in the past mechanical closures had to be used and fast intensity control was possible within certain limits only with mercury (Hg) lamps.
Another defect of existing transillumination systems concerns the fact that biological preparations often exhibit very poor contrast. As a result, many high quality transmitted light condensers are equipped for the possibility of contrast-amplifying processes, such as Zemicke phase contrast or Normarksi differential interference contrast. Both processes, however, require not only manipulation of the illumination light, i.e., the beam path in front of the specimen, but also the light after it passed through the specimen. To accomplish this, either special objective-lenses are necessary (phase contrast) or optical elements such as DIC prisms and analyzers must be placed in the beam path. Phase contrast objectives usually limit the choice of objectives and reduce light throughput to some extent, while optical elements such as analyzers requires for DIC reduce light throughput considerably. Consequently, fast switching between optimum, contrast-intensified transmitted light observation and weak-light fluorescence observation is not possible.
U.S. Pat. No. 4,852,985 discloses an illumination device for a microscope, which is made as a flat array of individually triggerable light emitting diodes, which overcomes some of the described problems.